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Making Strides Toward Low-Cost LED Lighting
Posted by
timothy
on Sun Jul 20, 2008 01:30 PM
from the brightly-walk-among-the-clouds dept.
from the brightly-walk-among-the-clouds dept.
Roland Piquepaille writes "You all know that incandescent bulbs are pretty inefficient, converting only 10% of electricity into light — and 90% into heat. Light-emitting diodes, or LEDs, could soon replace incandescent and compact fluorescent bulbs in our homes. They are more efficient and environmentally friendly. But LED lights are currently too expensive because they are using a sapphire-based technology. Now, Purdue University researchers have found a way to build low-cost and bright LEDs for home lighting. According to the researchers, the LED lights now on the market cost about $100 while LED lights based on their new technology could be commercially available within a couple of years for a cost of about $5. It would also help to cut our electricity bill by about 10%."
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A Super-Efficient Light Bulb 468 comments
Chroniton writes with news of a Silicon Valley company, Luxim, that has developed a tiny, full-spectrum light bulb, based on a plasma of argon gas, that gives off as much light as a streetlight while using less power. The Tic Tac-sized bulb operates at temperatures up to 6000K and produces 140 lumens/watt, almost ten times as efficient as standard incandescent lamps, and twice the efficiency of high-end LEDs. The new bulbs also have a lifetime of 20,000 hours. There's no mention of mercury or other heavy metals, which pose a problem for compact fluorescents.
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Light vs. heat scale (Score:3, Interesting)
LED = Luxury Goods (Score:5, Interesting)
Take a hint from the car manufacturers. Today, high-end cars are using LED tail lights. They are also used on trucks. The main advantage is they do not burn out.
However, for most people in the world a burned-out tail light bulb is a minor safety issue and a minor expense. Replacing the bulb takes 10 minutes and maybe the owner's manual if you are truely clueless about how to do it. Also, many people own a car for 5+ years without ever having to replace a single bulb.
Compare this to the cost of a minor traffic accident where a tail light is cracked. No, you cannot replace the lens or any individual part, just the whole assembly. Instead of $100-$200 for an incandescent bulb assembly expect to pay $1500-$2000 for the LED tail light.
Sure, over the life of many vehicles it is a minor issue that bulbs will never burn out. But over the same number of vehicles it is far, far more likely that a lamp assembly will have to be replaced. The result is a far more expensive part to replace.
With trucks there is a certain amount of sense to be made with claiming that the bulbs do not have to be replaced. Replacing a bulb on a truck or semi-trailer can be a real hassle requiring a ladder and tools. However, again the likelyhood the bulb would ever need to be replaced vs. the lens being damaged is about the same as for cars. Basically, it is a complete rip-off.
Expect to see wired-in LED systems in household lamps where the fixture must be replaced because the bulbs cannot be. Expect to see the fixtures sold to builders with non-replacable bulbs will cost the builder only slightly more when bought in huge quantities but the homeowner will be faced with $1000 lamp fixtures should they ever need or desire to replace them.
Re: (Score:3, Interesting)
Re:LED = Luxury Goods (Score:5, Informative)
Trucks use LED taillights because they are more visible in the daytime. It never ceases to amaze me how often a 4-wheeler (car driver) will rear-end a truck that is braking for a stoplight or turn, then claim that they didn't see the truck's brake lights.
The LED taillights you see on a lot of semi-trailers are held in place by metal bezels that are riveted in place by the manufacturer. To replace one, you have to drill out the rivets. Then of course you can simply use self-tapping screws to put the bezel back on once you have replaced the light. Incandescents tend to be held in place by a rubber cup-like thing that I don't know the name for, and can be removed by prying on the light with a flathead screwdriver, much like dismounting a tubeless tire from a wheel.
The reason for riveting the things in place is to deter theft. Incandescent lights don't get stolen nearly as often as LED's for some reason.
Parent
Re: (Score:3, Informative)
Take a hint from the car manufacturers. Today, high-end cars are using LED tail lights. They are also used on trucks. The main advantage is they do not burn out.
However, for most people in the world a burned-out tail light bulb is a minor safety issue and a minor expense. Replacing the bulb takes 10 minutes and maybe the owner's manual if you are truely clueless about how to do it. Also, many people own a car for 5+ years without ever having to replace a single bulb.
Compare this to the cost of a minor traffic accident where a tail light is cracked. No, you cannot replace the lens or any individual part, just the whole assembly. Instead of $100-$200 for an incandescent bulb assembly expect to pay $1500-$2000 for the LED tail light.
Sure, over the life of many vehicles it is a minor issue that bulbs will never burn out. But over the same number of vehicles it is far, far more likely that a lamp assembly will have to be replaced. The result is a far more expensive part to replace.
With trucks there is a certain amount of sense to be made with claiming that the bulbs do not have to be replaced. Replacing a bulb on a truck or semi-trailer can be a real hassle requiring a ladder and tools. However, again the likelyhood the bulb would ever need to be replaced vs. the lens being damaged is about the same as for cars. Basically, it is a complete rip-off.
Expect to see wired-in LED systems in household lamps where the fixture must be replaced because the bulbs cannot be. Expect to see the fixtures sold to builders with non-replacable bulbs will cost the builder only slightly more when bought in huge quantities but the homeowner will be faced with $1000 lamp fixtures should they ever need or desire to replace them.
I smell some FUD
As for the replacement cost of a LED light component on a car. I personally can replace BOTH left and right sides of my cars LED light assemblies (which consists of 4 separate pieces) for $450. The leap from incandescent assemblies is only about $100. And yes, this is OEM, not a 3rd party solution. And to top this off, it takes about the same 10 minutes to replace these assemblies.
As for it being a complete rip-off, the odds of it needing to be replaced is not the only implication. Most LED
Re:LED = Luxury Goods (Score:5, Interesting)
They are. I've seen some in nightclubs and at concerts, the brightness and the instant on/off effect is fantastic.
It's probably even better with ecstasy.
Parent
Don't market these in Boston (Score:4, Funny)
They really have a phobia about LEDs there- especially if there are wires attached like an AC cord.
It's Roland the Plogger, wrong as usual (Score:4, Interesting)
It's so Roland the Plogger.
The "breakthrough" this time is that someone made gallium nitride substrates that might, someday, be useful for LEDs. After they solve the problem that their material cracks during cooling. However, Panasonic did that last year [compoundse...ductor.net], and has been shipping white LEDs using that approach in sample quantities.
Re:It's Roland the Plogger, wrong as usual (Score:5, Insightful)
Parent
Re: (Score:3, Informative)
You're missing the "Roland Piquepaille" link just on top of the summary.
Re:It's Roland the Plogger, wrong as usual (Score:4, Insightful)
Ya know, the whole Roland thing has been kicking around for a few years, and I'm starting forget why I was ever annoyed with him. I mean, really, how is what Roland does different from what Slashdot itself does? He's finding content and pointing it out to us. Slashdot does the same thing. He gets ad profit from hits. So does /. Big deal.
So, what is the big deal? Sure, someone did something similar last year. I'll clue you in to something: someone has always done something similar last year. It's called science. It's mostly evolutionary, not revolutionary. And do you really have to dis what the Purdue folks have done just because you're annoyed with Piquepaille? That's kinda petty, bubba.
Parent
$100,00 - no way (Score:3, Insightful)
Electricity savings ? (Score:5, Informative)
I realise it's customary not to RTFA, but I would think that the submitters would at least read what they submit. Roland wrote:
The article says:
Far from the same thing. But I suppose that's another reason people don't like Roland.
Do LEDs blink ? (Score:5, Interesting)
So, suck it up, I hear you say. Right, except that each blink leaves an annoying remanent patch on my retina that lasts for a few seconds. Imagine driving at night in a city, 10 cars in your field of vision, look left, right and suddenly you have 200 spots in your field of vision. Awesome to know what's going on, right ?
I loathed the xenon high beams when they first came out a few years ago. You know, those tiny very concentrated blue lights ? Leaves a retina trail that lasts for 20 seconds. I'm so glad that they are gone now. I've never heard if they were made illegal or if they just went out of fashion, but I hope LEDs (which are a good technology) are applied in a good way...
Re:Do LEDs blink ? (Score:4, Informative)
Yes, the only way to vary the brightness reliably is to use PWM (Pulse width modulation, aka "duty cycle"). There is some variance from voltage, but the best way is to operate them at a constant voltage.
All "breathing" LEDS (like on sleep mode for laptops) is accomplished this way. Duty cycle is controlled by a simple sin() or cos() function.
Parent
Re:Do LEDs blink ? (Score:5, Informative)
I loathed the xenon high beams when they first came out a few years ago. You know, those tiny very concentrated blue lights ? Leaves a retina trail that lasts for 20 seconds. I'm so glad that they are gone now. I've never heard if they were made illegal or if they just went out of fashion [snip]
Xenon HID headlights never went away. They're still standard equipment on higher end Japanese and some German luxury cars and optional on many others. If anything, their use by car manufacturers are expanding, not contracting.
What YOU'RE complaining about, and thankfully seem to have gone away, are those high intensity blue color lights that dropped into a standard headlight assembly. Like you mention, I don't know if they were made illegal or became "uncool" but I hated them as well. True Xenon HIDs have a completely different reflector assembly than standard halogen headlights and spread the light far more evenly and are actually less annoying that a slightly misaimed halogen headlight, and you probably see them all the time and don't even realize it. They look "blue" only compared to what turns out to be the yellow tinge of a regular headlamp, but at a glance just appear very white.
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Re:Do LEDs blink ? (Score:5, Interesting)
What you are seeing is the pulse-width-modulation dimming of the taillights applied with insufficiently high frequency. Cheap chinese flashlights like the Jetbeam C-LE (which has gone through three revisions prior to current - and is an absolutely excellent little LED torch) have been using increasingly high PWM frequencies to get around that; more expensive ones use current regulation (which averages the current of the PWM circuit over a few tenths of a second to produce a flat current (and therefore brightness) curve when viewed on an oscilloscope. The advantage of lower PWM frequencies is that the eye hands them off to the brain via a high-priority nerve link that results in people noticing them significantly (tenths of a second or so, IIRC) faster, theoretically reducing both the number and severity of accidents. The fact that many of them are bright enough to impair normal night vision seems to be lost on auto designers.
HID headlights have not gone away, but their implementations have been getting better - projecting beams on a down-angle so they don't nail people in the eyes, lowering the operating temperature of the bulb, making them less blue and more yellow-white without making them dimmer (actually, lower-temperature HID bulbs are more efficient than the blue-tinted ones). HIDs are popular for bulb life being insane, since headlight replacement was getting to be a significant drain in carmaker's warranty claims, and being brighter and having a longer effective range, which is good when there's no streetlights.
Entirely different is the blue-tinted halogen bulbs that are simply normal bulbs with a light blue paint applied - these are the ghetto-fabulous attempt to make it look like you've got an expensive HID conversion for an older car, and are about 30% dimmer than normal halogen headlights despite being harder on other drivers' eyes. I have no forgiveness for people who use these because they think it looks good.
Parent
many advantages (Score:4, Informative)
LED light bulbs are coming along. I've been keeping my eye on the GeoBulb sold by C Crane, but it's about $120 and always seems to be listed as out of stock. It is available in three color temperatures, however, so perhaps that's been worked out. There are a few others, including some T8 replacements. Unfortunately, they're all expensive and the ones that fit standard sockets max out at about the equivalent of a 60 watt incandescent. But these things will get worked out. On the plus side, advantages include not just electrical savings and longevity, but also less heat (less risk of fire) and less vulnerability to things like vibration and moderate temperature changes. Unlike compact fluorescents, they contain no mercury and turn on/off instantly. I believe some are dimmable, but I'm not sure. In any case, it seems clear that it will only take a few years of fairly routine development for LED bulbs to be much more practical than all the alternatives. There doesn't seem to be a down side.
The summary would seem to imply only modest electrical savings. I'm pretty sure the 10% figure just reflects the fact that light bulbs are only part of your electrical picture. The rated wattage for a 60-watt equivalent is about 8 watts. Correcting for overoptimism, that's about 80% savings wherever you plug one of these in.
LED already cost-effective in some situations (Score:5, Informative)
If you have a large number of low wattage/low voltage light sources, CFL is not viable, but LED is. The power requirements are so much lower that smaller transformers can be spec'd, you can string piles more of them on a circuit, saving even more money.
There are some neat bulbs available at http://www.theledlight.com [theledlight.com].
Enjoy your LED lights now, (Score:4, Informative)
because they aren't going to exist much longer into the future. http://www.idtechex.com/products/en/articles/00000591.asp [idtechex.com]
I also find it ironic that everyone seems to love that mercury is not contained in LED's, yet is it essential to the extraction of gallium from ore.
Re:Yea, (Score:4, Informative)
They will be way more environmentally friendly. No mercury involved.
Parent
Re:Yea, (Score:4, Informative)
I have a new way to deal with Roland Piquepaille spam, every time I see an article by him I go away for 3 days.
So, see you on the 24th...
Parent
Re:Yea, (Score:4, Informative)
No mercury = huge improvement
Parent
Re:Yea, (Score:5, Informative)
But how much of an improvement will they be over fluorescent lights, which we already have at an affordable price?
Well, they won't flicker, they won't contain mercury, and they won't be too big to fit in many light fixtures.
Even if LEDs aren't any more efficient than current CFLs, they'll be a lot more attractive to people who don't like or can't use fluorescent lights.
Parent
Re:Yea, (Score:5, Informative)
Another article http://pubs.acs.org/isubscribe/journals/cen/86/i28/html/8628cover4.html [acs.org] provides some interesting information on organic LEDs - OLEDs have interesting design applications since you can make them in flat sheets
(I think an illuminating wall would be way cool, but maybe thats just me :-))
Right now efficiencies are similar to the inorganic LEDs and fluorescent bulbs.
Parent
Re:Yea, (Score:5, Interesting)
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Re:Yea, (Score:4, Informative)
They are already more efficient. I have a 3W MagLite that runs on 2AA and will blind you.
Mercury in the CFL's are not as much of a concern as mercury in those 4' flouro's of the commercial buildings, but maybe they are more likely to be recycled.
Eating tuna might be more of a problem though.
http://www.gotmercury.org/article.php?list=type&type=75 [gotmercury.org]
Parent
Re:Yea, (Score:4, Insightful)
Intensity and light output are two different things. LED lighting doesn't exceed the efficiency of fluorescent lighting in terms of lumens per watt yet. Many LED manufacturers continue to announce products they claim exceed the efficiency of fluorescent lighting, but they haven't actually managed to do it yet. That said, they're getting very close.
Parent
Re:Yea, (Score:4, Informative)
LED lighting doesn't exceed the efficiency of fluorescent lighting in terms of lumens per watt yet.
Your description of the problem displays a level of ignorance which could easily be corrected by simply reading wikipedia. The simple truth is that there are numerous LED lights which are more efficient than flourescents, but there is a very good reason why the bulk of them are not.
This reason is that white LEDs are fluorescent lights [reference.com]. Not all of them, but all the cheap ones. That's because the alternative is to use multiple junctions in a package to produce a mixture of light to produce the whitest possible light. There are bicolor and tricolor (and for all I know quadcolor) LEDs, some of which are tuned for the closest thing you can get to white, and some of which are tunable.
The typical white LED is a blue LED (the most expensive single-color visible LED) doped with a material which emits yellow light when the blue light strikes it. This method does not produce the brightest light nor the whitest, but it is by far the cheapest way to produce a "white" LED.
The 3W mag-lite may not be more efficient than an imaginary flourescent that would produce the same amount of light, but they do illustrate a different point; the flourescent has a glass tube filled with toxic shit and a ballast to drive it. You can build the voltage regulation hardware right into an LED and just hook it up to some LVDC. I would be extremely amazed if the total lifetime energy cost of flourescent lighting were not significantly higher than that of LED lighting.
In short, [typical] white LEDs are not more efficient than fluorescent lighting because they are fluorescent lighting. When the cost of blue LEDs come down, and tricolor LEDs become more ubiquitous, then the price of the more-efficient "white" (in this case, tricolor) LED lighting will come down.
Parent
Re:Yea, (Score:5, Informative)
2003 called, it wants it's CFL stereotypes back.
CFLs don't flicker like old ballast-type fluorescent tubes of decades ago. And the newer ultra-compact ones are actually smaller than the incandescent bulbs they replace. I have one in the swing-arm desk lamp in front of me right now, and the tip of the bulb no longer protrudes past the end of the shade like the old bulbs I used in it long ago. In my bathroom I have CFL bulbs made to look identical to G25 globe lights, in the same fixture with the actual incandescent bulb I am slowly replacing. They appear the same except the CFLs are brighter and their light isn't as yellow.
I will give you the mercury, though.
Parent
Re:Yea, (Score:5, Informative)
The question is really, whether you prefer 2.4mg of mercury in air plus 2mg in the landfills, or more than 2.4mg of mercury in the air. Until LEDs become more efficient than CFLs, I'll opt for CFLs.
Note, there is a confusion over LED vs CFL efficiency. LEDs generate light more efficiently than CFLs, but they do so in a narrow arc. To make it useful for everday applications conversion to a wider arc takes place and that causes efficiency loss.
Parent
dental fillings (Score:4, Interesting)
That's all well and good but you would be surprised at how much mercury gets into the environment from dental fillings and how few people will pay the extra $15.00 to get composite fillings!
Not everyone knows dental fillings contain mercury. I got into an argument with someone over that, I had to prove to them mercury was used. And not all dentists use composite fillings [wikipedia.org].
Falcon
Parent
Re:Yea, (Score:4, Insightful)
>CFLs don't flicker...
CFLs cause me migraines and other visual problems. I recently changed all my home lighting, where possible, to CFLs.
After a week, I began suffering from an extreme migraine. As the CFL's made it difficult for me to read or focus on small objects - I instantly held them suspect. To test my theory, I changed all the lighting back, and by the next day my life had certainly improved.
I gave it a month and tried the CFL's again, and again after a week a migraine set in. I intend to remove them tomorrow. My girlfriend (as in a living 3D female human-being [facebook.com]) who doesn't normally suffer from migraines has been complaining of symptoms while I had the CFLs in.
I think CFLs definitely have a use but not as a be all and end all of general home lighting. The most pleasant affordable technology for me is halogen lighting. I am looking forward to what LED and OLED technology has to offer in the near future.
--
Deceive the rich and powerful if you will, but don't insult them.
Parent
Re:Yea, (Score:4, Informative)
The LF version flickers with 50 or 60 Hz (depending on where you live) while the HF version has a lot higher frequency and will be almost flicker-free.
LED:s also suffers from flickering if you feed them with AC, but if you use DC and a low-pass filter you will get rid of the flickering.
The color spectrum is also different depending on the type of light source.
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CFL Color (Score:5, Interesting)
I really like the color you get when a 2700 & 5000 degree light are in the same fixture, everything looks bright and colorful.
Parent
Re:CFL Color (Score:4, Informative)
Perceptions.
Direct unfiltered sunlight indoors doesn't look yellow, it's almost pure white.
Sun's spectrum is very close to the ideal black-body spectrum with the color temperature is about 5000K. So 5000K CFL will look almost exactly like the real sunlight.
Parent
Re:CFL Color (Score:5, Informative)
Not perceptions... Quanta [wikipedia.org]
Look at the sun and at a CFL though a spectroscope. With the sun, you'll see even intensity across the spectrum. When you look at the CFL, you'll see several distinct bars of light at specific wavelengths. While both average out to about the same color temperature, the sun will have a black-body spectrum, evenly illuminating the pigments in the items in your room, while the CFL will make certain colors in the room jump out more than others.
Parent
Re:CFL Color (Score:5, Interesting)
Here's some links:
A white LED's spectrum [sci-toys.com]
A CFL's spectrum [sci-toys.com]
Parent
Re: (Score:3, Informative)
I bought mine at Wal-Mart. They're GE brand and were right next to their older, longer GE bretheren on the display. The package said "Smaller Size" right on it in big letters. They came in a two pack instead of a three, and they are more expensive than the older ones. But they also put out a few lumens more (not much, but still slightly higher) than the longer ones, even though they were both rated for the same "incandescent watt" equivalent. They are rated for longer life though, 10,000 hours verses 8,000
Re: (Score:3, Interesting)
I've never had a CFL burnout
They will do. My parents were early adopters (must be over 15 years since we had them), I think the only incandescent light in their house is in the microwave.
I remember the first ones cost about £10 and were massive, heavy things and they did flicker, and take five minutes to warm up. But the ones made in the last 5 years or more are brighter, white, don't flicker, and don't buzz. They do (eventually) burn out though.
Yellowy incandescent lights remind me of my grandma's house; admittedly the ye
Re:Yea, (Score:5, Interesting)
Well, they won't flicker, they won't contain mercury, and they won't be too big to fit in many light fixtures.
Even if LEDs aren't any more efficient than current CFLs, they'll be a lot more attractive to people who don't like or can't use fluorescent lights.
Have you actually looked at high-quality CFL bulbs? A good daylight bulb is a thing of beauty. No flicker (and, you know, CFL bulbs have never had flicker because they are run at much, much higher frequencies than you visual sytem can see), proper color balance, small, reliable, quiet.
Note that I'm not talking about the two or four foot long fluorescent bulbs that you might have in your office. Those are probably not daylight balanced and probably flicker at 120 Hz (yes, 120 Hz, not 60 Hz, because both half cycles push current; unless you're in part of the world which runs on 50 Hz mains, in which case they flicker at 100 Hz). Their ballasts also have a tendency to buzz.
Good CFLs are wonderful.
Note, also, that many LED bulbs you can get these days are simply awful because they flicker at 60 Hz (yes, 60 Hz, because they're arranged in cascading diode fashion and only conduct on every other half cycle) and the phosphors are terrible. They also lose brightness at an astonishing rate and are horribly temperature sensitive (hotter chip, lower light output). The 60 Hz issue can certainly be fixed with better circuitry (ie, bridge rectifiers and some low-pass filtering) and one hopes that the phosphors and lifetime improve.
Wait, phosphors in an LED? What am I smoking? Yes, it's true, most white LED bulbs for sale are actually UV emitters that excite phosphors. And just like fluorescents, the better the phosphors, the better the output spectrum. While it is possible to generate white-ish light from a combination of red, blue, and green LEDs, because the aging curves are different for the three classes of emitters, the color balance is dynamic over the bulb lifetime. And, also, the spectrum is terrible -- even the spectrum from fluorescents is better -- because it's essentially three isolated wavelengths instead of a continuous spectrum.
LEDs have a long, long way to go before they can be used in living or working spaces.
Parent
Re:Yea, (Score:5, Informative)
In addition the no mercuary as already noted, they will have a longer life, be less fragile, and be smaller.
Parent
Re: (Score:3, Informative)
They'll also have a longer lifetime than CFLs. The article says they could last as long as 15 years, compared to CFLs which I believe have an expected life of about 7 years.
Re:Yea, (Score:4, Interesting)
Poster saith:
TFA saith:
Me: "I live in Canuckistanbul - we NEED the heat, you ignorant clods!"
Electricity costs less than oil or gas here ... it's cheaper to get some extra BTUs from incandescents in the winter months ...
Parent
Re:carbon-free daytime lighting (Score:4, Funny)
With the cost of solar cells and LEDs plummeting, a solar cell roof installation with closed-circuit LEDs might soon become cheaper than a ceiling window.
What do you know! Soon enough it'll all get so efficient that with closed-circuit LEDs shining on solar cells you'll be able to make your own infinite source of energy!!
Oh shit that's a hell of good idea! The first one to the patent office wins!!
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Re:Is it white, though? (Score:5, Informative)
Having three Red Green Blue LEDs to create white light might produce a light that appears white to the eye, but might not have the same effect when reflected off material.
The white from the phosphor would generate more of a broad spectrum white, whereas the Red, Green and Blue LEDs would probably create spikes in the Red, Green and Blue spectrum.
So you might have a green material that appears black when you use the "RGB white" LED - just because it does not reflect the Green LED's narrow green, whereas it will appear green in the white from the phosphor white LED.
The phosphor means one more step in light conversion, and that probably means less efficiency.
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Re:Is it white, though? (Score:5, Informative)
As far as I know, the most used variant is the blue LED + yellow phosphor one. In this case, the blue light, emitted by the LED, is cast directly, besides the yellow light coming from the phosphor. The mix of blue and yellow produces white light.
Unfortunately, these LEDs don't produce a very broad spectrum of light either. The spectrum has a sharp peak in the blue range, and a bit broader yellow range, as can be seen on this graph on the Wikipedia page [wikipedia.org].
Parent
Re: (Score:3, Informative)
I would have absolutely agreed a few years ago. Traditional fluorescents hurt my eyes after a while, and incandescents are slightly warmer, and yellower, like natural light. However, the new compact fluorescents are awfully good, and with certain ones I can't tell the difference between them and incandescent bulbs.
Re:Concerns about LEDs... (Score:4, Informative)
Can LED's be dimmed? As far as I've seen it's not possible.
Not so. LEDs can be dimmed either by regulating the forward DC current (then they don't flicker at all) or by pulse-modulating some fixed current; the LEDs in the latter case will flicker only if the frequency of the pulses is too low. LEDs have very low capacitance and inductance, so they can be easily pulsed with any high frequency of your choice, though 1 kHz would be more than enough. And as I said the DC source works also.
Parent
Link (Score:3, Interesting)
Luxim Plasma [treehugger.com]